1. Field of the Invention
The present invention relates to an air conditioner, which is designed to carry out a defrosting operation for an outdoor heat exchanger by circulating refrigerant therein.
2. Description of the Related Art
Generally, a heat pump type air conditioner carries out a cooling operation or a heating operation in such a way that a flowing direction of refrigerant discharged from a compressor is converted by controlling a four-way valve connected to a discharging outlet of the compressor.
A multi air conditioner, which is adapted to carry out an air conditioning operation for a plurality of rooms, includes a single outdoor unit and a plurality of indoor units connected to the outdoor unit. In the multi air conditioner, a load required by the plurality of indoor units frequently fluctuates, and a range of the fluctuation is broad. Accordingly, since the air conditioner must be equipped with a high-capacity and expensive compressor in order for the single outdoor unit to satisfy a cooling load (or a heating load) required overall by the indoor units, an economical burden is accompanied.
Considering the situation, the air conditioner may be provided with a plurality of outdoor units, to positively cope with the fluctuation of the load required by a plurality of indoor units. Furthermore, pipes connected to the plurality of outdoor units may be shared by the plurality of indoor units, to reduce the pipes transferring the refrigerant.
As the multi air conditioner is operated in a heating mode, heat exchangers of the outdoor units are frosted, thus lowering an efficiency of heat exchange. To prevent the efficiency of heat exchange from declining, the multi air conditioner is operated in a defrosting mode.
In the conventional multi air conditioner, when only one of the plurality of outdoor units is intended to carry out a defrosting operation, the other remaining outdoor units are also set to be operated in the defrosting mode. That is, even if only one outdoor unit in question is required to be operated in the defrosting mode, the other remaining outdoor units must be operated in the defrosting mode together with the one outdoor unit, thereby increasing the number of the defrosting operations carried out. In addition, since outdoor units, which are operating in the heating mode, must be converted into the defrosting mode after the heating mode is stopped, a heating capacity of the multi air conditioner is decreased.